Sleep apnea is a condition in which a person stops breathing for a short time while sleeping. Symptoms of sleep apnea include snoring, breath holding during sleep, rapid awakening with gasping for air, morning headaches, depression, irritability, loss of memory, lack of energy, high risk of automobile and workplace accidents, and lack of high quality sleep and resulting daytime grogginess and sleepiness. Sleep apnea is rarely fatal but is linked to high blood pressure and increased probability of heart disease, stroke, and arrhythmias. Patients with coronary artery disease who have a blood oxygen level lowered by sleep-disordered breathing may be at risk of ventricular arrhythmia and nocturnal sudden death. Furthermore, sleep-disordered breathing may cause coronary artery disease and hypertension.
There are different classifications of sleep apnea depending upon the source of dysfunction. Obstructive sleep apnea results from mechanical blockage of the airway, for example, due to weight of fatty neck tissue compressing the trachea or decrease of muscle tone during sleep. Central sleep apnea results from neurological dysfunction. Another reason for central sleep apnea is lung-to-chemoreflex CO2 sensor located in carotid body. The decreased cardiac output will delay the circulatory time which affect the feedback delay time resulting oscillatory behavior in respiratory controller.
Various treatments exist for sleep apnea including medical device treatments, surgery, and drugs. The type of treatment depends on the classification of sleep apnea. For patients who also experience heart failure or other cardiac conditions, implantable cardiac devices (e.g., implantable pacemaker or defibrillator) have been proposed for treating sleep apnea through the use of high rate pacing therapy. It would be advantageous for such devices to be capable of differentiating between central sleep apnea and obstructive sleep apnea for diagnostic purposes or to administer the appropriate responsive therapies.